[NH2:1][C:2]1[CH:11]=[CH:10][C:9]2[C:4](=[N:5][C:6](Cl)=[CH:7][CH:8]=2)[N:3]=1.[CH3:13][N:14]([CH3:19])[CH2:15][CH2:16][CH2:17][SH:18].[OH-].[K+].CS(C)=O>C(OCC)C.O>[NH2:1][C:2]1[CH:11]=[CH:10][C:9]2[C:4](=[N:5][C:6]([S:18][CH2:17][CH2:16][CH2:15][N:14]([CH3:19])[CH3:13])=[CH:7][CH:8]=2)[N:3]=1
A mixture composed of 2-amino-7-chloro-1,8-naphthyridine (8 g), 3-dimethylaminopropanethiol (11.4 g), potassium hydroxide pellets (85% pure; 6.26 g) and dimethyl sulphoxide (87 cc) is heated to 90° C. for 3 hours 30 minutes. The reaction mixture is then poured into water (1500 cc) and extracted with methylene chloride (5×400 cc). The organic extracts are combined and washed with distilled water (400 cc), dried over magnesium sulphate and concentrated to dryness at 40° C. under reduced pressure (4 kPa). The residue obtained is treated with ethyl ether (100 cc). The insoluble product is separated by filtration, washed with ethyl ether (10 cc) and dried at 40° C. under reduced pressure (0.07 kPa). 2-Amino-7-(3-dimethylaminopropylthio)-1,8-naphthyridine (9 g), m.p. 164° C., is obtained.
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